There are two kinds of speed changers of conventional motorized treadmills. One changes the speed of the treadmill by adjusting the distance between the belt pulleys on the motor shaft and the treadmill roller. Obviously, this kind of speed changer has the following disadvantages: (1) Without the help of another person, it is impossible for the operator to turn the screw rod when running. (2) It needs a motor of greater power, namely, it consumes more electricity. (3) Its motor can not be started loadlessly because it has no separating mechanism. So elastic fatigue and slip will occur to the belt after being in tension for a long time and adjusted frequently. As a result, the life of motor and belt will be reduced. (4) It is not suitable for use by old people and patients who are recovering from illness because it can not be started from zero speed.
Another changes the speed of the treadmill by changing its voltage. This kind of motorized treadmill can be started from zero speed but the structure is too complicated. The need of motor of greater output results in higher consumption of electricity and the high cost of construction reduces its competitiveness.
In view of these disadvantages, the inventor tried hard to make improvements and developed the improved motorized treadmill speed changer which can be started from zero speed and change speed steplessly and freely.
So the main object of this invention is to provide an improved motorized treadmill speed changer of which the speed of the revolving belt can be changed easily by adjusting the engaging point of the friction cone on the motor shaft and the friction wheel on the roller of the treadmill.
Another object of this invention is to provide an improved motorized treadmill speed changer which has a greater speed range and is suitable for use by people of different physical conditions.
Still another object of this invention is to provide an improved motorized treadmill speed changer which can be started from zero speed and reach a speed as high as 1:1 (1 rotation of the motor shaft to 1 rotation of the roller of the treadmill).
Still another object of this invention is to provide an improved motorized treadmill speed changer of which the motor is of smaller power and is carried by a slide on a U support so that the cost of the treadmill can be reduced.